Four fire engines and around 25 firefighters were called to a fire at a single-storey car showroom and workshop on Pinner View in Harrow.
Part of the ground floor of the building was damaged by fire. A man and a woman were treated on scene by London Ambulance Service crews after suffering from smoke inhalation.
A London Fire Brigade spokesperson said: “There was a lot of smoke in the area on arrival coming from tyres which were alight.
“Crews worked incredibly quickly to gain access and bring the fire under control.”
The Brigade was called at 1046 and the fire was under control by 1127. Fire crews from Northolt and Wembley fire stations attended the scene.
The cause of the fire has been recorded as undetermined.